win32平台下通过WinSock2用C++实现一个非阻塞模式TCP客户端

好的，以下是一个简单的非阻塞模式TCP客户端的C++代码实现：

首先，我们需要包含WinSock2.h头文件和Windows.h头文件，并链接ws2_32.lib库文件：

#include <WinSock2.h>
#include <Windows.h>
#pragma comment(lib, "ws2_32.lib")

然后，我们需要初始化WinSock2库：

WSADATA wsaData;
int ret = WSAStartup(MAKEWORD(2, 2), &wsaData);
if (ret != 0) {
    printf("WSAStartup failed with error %d\n", ret);
    return -1;
}

接下来，创建一个socket：

SOCKET clientSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
if (clientSocket == INVALID_SOCKET) {
    printf("socket failed with error %d\n", WSAGetLastError());
    WSACleanup();
    return -1;
}

然后，将socket设置为非阻塞模式：

u_long iMode = 1;
ret = ioctlsocket(clientSocket, FIONBIO, &iMode);
if (ret != NO_ERROR) {
    printf("ioctlsocket failed with error %d\n", ret);
    closesocket(clientSocket);
    WSACleanup();
    return -1;
}

接下来，定义服务器的地址和端口号：

const char* serverAddr = "127.0.0.1";
const int serverPort = 12345;

创建一个sockaddr_in结构体，用于存储服务器的地址和端口号：

sockaddr_in serverAddrIn;
serverAddrIn.sin_family = AF_INET;
serverAddrIn.sin_addr.s_addr = inet_addr(serverAddr);
serverAddrIn.sin_port = htons(serverPort);

然后，连接服务器：

ret = connect(clientSocket, (sockaddr*)&serverAddrIn, sizeof(serverAddrIn));
if (ret == SOCKET_ERROR) {
    if (WSAGetLastError() != WSAEWOULDBLOCK) {
        printf("connect failed with error %d\n", WSAGetLastError());
        closesocket(clientSocket);
        WSACleanup();
        return -1;
    }
}

由于是非阻塞模式，所以连接函数可能会返回WSAEWOULDBLOCK错误，这是正常情况。

接下来，我们需要使用select函数来检查连接是否完成：

fd_set writeSet;
FD_ZERO(&writeSet);
FD_SET(clientSocket, &writeSet);

timeval timeVal;
timeVal.tv_sec = 5;
timeVal.tv_usec = 0;

ret = select(0, NULL, &writeSet, NULL, &timeVal);
if (ret == SOCKET_ERROR) {
    printf("select failed with error %d\n", WSAGetLastError());
    closesocket(clientSocket);
    WSACleanup();
    return -1;
}
else if (ret == 0) {
    printf("select timed out\n");
    closesocket(clientSocket);
    WSACleanup();
    return -1;
}

如果连接完成，writeSet中的clientSocket将变为可写状态。

最后，我们可以向服务器发送数据：

char* sendData = "Hello, server!";
int sendLen = strlen(sendData);

ret = send(clientSocket, sendData, sendLen, 0);
if (ret == SOCKET_ERROR) {
    printf("send failed with error %d\n", WSAGetLastError());
    closesocket(clientSocket);
    WSACleanup();
    return -1;
}

完整的代码如下：

#include <WinSock2.h>
#include <Windows.h>
#pragma comment(lib, "ws2_32.lib")

int main() {
    WSADATA wsaData;
    int ret = WSAStartup(MAKEWORD(2, 2), &wsaData);
    if (ret != 0) {
        printf("WSAStartup failed with error %d\n", ret);
        return -1;
    }

    SOCKET clientSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
    if (clientSocket == INVALID_SOCKET) {
        printf("socket failed with error %d\n", WSAGetLastError());
        WSACleanup();
        return -1;
    }

    u_long iMode = 1;
    ret = ioctlsocket(clientSocket, FIONBIO, &iMode);
    if (ret != NO_ERROR) {
        printf("ioctlsocket failed with error %d\n", ret);
        closesocket(clientSocket);
        WSACleanup();
        return -1;
    }

    const char* serverAddr = "127.0.0.1";
    const int serverPort = 12345;

    sockaddr_in serverAddrIn;
    serverAddrIn.sin_family = AF_INET;
    serverAddrIn.sin_addr.s_addr = inet_addr(serverAddr);
    serverAddrIn.sin_port = htons(serverPort);

    ret = connect(clientSocket, (sockaddr*)&serverAddrIn, sizeof(serverAddrIn));
    if (ret == SOCKET_ERROR) {
        if (WSAGetLastError() != WSAEWOULDBLOCK) {
            printf("connect failed with error %d\n", WSAGetLastError());
            closesocket(clientSocket);
            WSACleanup();
            return -1;
        }
    }

    fd_set writeSet;
    FD_ZERO(&writeSet);
    FD_SET(clientSocket, &writeSet);

    timeval timeVal;
    timeVal.tv_sec = 5;
    timeVal.tv_usec = 0;

    ret = select(0, NULL, &writeSet, NULL, &timeVal);
    if (ret == SOCKET_ERROR) {
        printf("select failed with error %d\n", WSAGetLastError());
        closesocket(clientSocket);
        WSACleanup();
        return -1;
    }
    else if (ret == 0) {
        printf("select timed out\n");
        closesocket(clientSocket);
        WSACleanup();
        return -1;
    }

    char* sendData = "Hello, server!";
    int sendLen = strlen(sendData);

    ret = send(clientSocket, sendData, sendLen, 0);
    if (ret == SOCKET_ERROR) {
        printf("send failed with error %d\n", WSAGetLastError());
        closesocket(clientSocket);
        WSACleanup();
        return -1;
    }

    closesocket(clientSocket);
    WSACleanup();

    return 0;
}

希望对你有所帮助！